KR20230135901A - Green emitting lead-free metal halide compound and method for manufacturing the same - Google Patents

Abstract

A metal halide and a method for producing the same are provided. The metal halide includes a compound represented by the following formula (1), has an orthorhombic crystal structure, and has a space group of Pnma:
[Formula 1] A ₂ Mn(X ¹ _1-a X ² _a ) ₄
In Formula 1, A is an alkali metal element, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3.

Description

Green emitting lead-free metal halide compound and method for manufacturing the same}

The present invention relates to a light emitting body, and more specifically to a lead-free metal halide light emitting body.

The liquid crystal display (LCD) industry is improving the efficiency of LCDs and improving their color gamut (the color content of displays) to compete with organic light-emitting diode displays (OLED) products. We are looking for solutions that Conventional LCDs lag behind OLEDs, especially in color gamut performance. The use of quantum dots (QDs) in LCDs has improved the color gamut performance of LCDs.

Recently, perovskite material, which has been in the spotlight, has various band gaps and corresponding color control by controlling halogen elements, high photoluminescence quantum yield (PLQY), and a narrow full width at half width of ~20 nm. maximum, FWHM). It is known that by applying this to the color filter of the LCD, an LCD with high color purity and high color reproducibility can be achieved.

However, perovskite with high performance contains lead (Pb) as a metal cation. In the European Union, the use of hazardous heavy metals, including lead, in electronic devices is regulated by the Restriction of Hazardous Substances Directive (RoHS), and other countries are expected to gradually introduce such regulations.

The problem to be solved by the present invention is to obtain a lead-free luminous body that does not contain lead and has excellent optical properties.

In order to achieve the above technical problem, an embodiment of the present invention provides a metal halide. The metal halide includes a compound represented by the following formula (1), has an orthorhombic crystal structure, and has a space group of Pnma:

[Formula 1]

A ₂ Mn ₍ X ¹ _{1 -} ^a

In Formula 1, A is an alkali metal element, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3.

The compound represented by Formula 1 may be a compound represented by Formula 2 below:

[Formula 2]

Cs ₂ Mn(X ¹ _1-a X ² _a ) ₄

In Formula 2, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3.

In Formula 2, a may be greater than 0 and less than 0.3. Specifically, in Formula 2, a may be 0.01 to 0.2, and more specifically, 0.05 to 0.15.

The compound may have the same crystal structure as β-K ₂ SO ₄ . Specifically, the compound may have a crystal structure with Mn ^{2+ at} the center and MnX ⁴ tetrahedra with _four X ¹ , there is.

The compound can emit light in the green region by dd transition between ⁴ T ₁ and ⁶ A ₁ levels.

The compound may be glass ceramic.

In order to achieve the above technical problem, an embodiment of the present invention provides a color conversion method. The color conversion method includes obtaining light in the green region by irradiating incident light in the ultraviolet to blue region to the compound represented by Formula 1. The incident light may be light of 370 to 490 nm.

In order to achieve the above technical problem, an embodiment of the present invention provides an optical device. The optical element includes a blue light emitting layer; and a layer containing the compound represented by Formula 1 disposed on the blue light-emitting layer. The optical element may be a backlight unit (BLU) or a display.

In order to achieve the above technical problem, an embodiment of the present invention provides a method for producing a metal halide. First, the raw materials AX ¹ , AX ² , MnX ¹ ₂ , and MnX ² ₂ are mixed in a stoichiometric equivalent ratio to obtain a mixture. It includes the step of calcining the mixture in an inert gas atmosphere or reducing atmosphere and then naturally cooling to obtain a compound according to the following formula (1), wherein the compound has an orthorhombic crystal structure and a space group of Pnma. A metal halide is prepared having:

A ₂ Mn ₍ X ¹ _{1 -} ^a

In Formula 1, A is an alkali metal element, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3.

The firing can be performed by raising the temperature to 600 to 700°C and maintaining it for 10 to 25 hours.

_The ^{X is a different} _halogen element ^of X ¹ and This is the step of obtaining a mixture by mixing at a molar ratio of a:a, and the compound represented by Formula 1 may be a compound represented by Formula 2 below:

[Formula 2]

Cs ₂ Mn(X ¹ _1-a X ² _a ) ₄

In Formula 2, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3.

The metal halide according to an embodiment of the present invention can exhibit excellent optical properties, particularly excellent luminous efficiency, color purity, and stability, without containing lead.

The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

Figure 1 shows the crystal structure of the compound represented by Formula 1 or Formula 2.
Figure 2 shows the crystal structure (a), electronic configuration in the valence band (VBM) and conduction band (CBM), and electronic density of state (density of state) of Cs ₂ MnBr ₄ according to an embodiment of the present invention. DOS) (c), and band gap (d) are shown.
Figure 3 is a schematic diagram showing the emission color according to the crystal field force (△) for each polyhedral structure of Mn ²⁺ ions.
Figure 4 shows optical photos taken before and after pulverization after cooling during the manufacturing process of the Cs ₂ MnBr ₄ phosphor powder of Preparation Example 1.
Figure 5 shows a TEM (Transmission Electron Microscope) image (a), a lattice fringe image (b), and a Selected Area Electron Eiffraction pattern (SAED pattern) (c) of the Cs ₂ MnBr ₄ phosphor particles of Preparation Example 1. and EDX mapping (Energy-dispersive X-ray mapping).
Figure 6 shows Cs ₂ Mn (Br _1-a Cl _a ) 4 of Preparation Examples 1 to ₄ (a=0, 0.1, 0.2, and 0.3) shows the X-ray diffraction pattern for the phosphor powder.
Figures 7 and 8 show Cs ₂ Mn (Br _1-a Cl _a ) ₄ of Preparation Examples 1 to 4, respectively. (a=0, 0.1, 0.2, and 0.3) This is a graph showing the optical properties of the phosphor powder and a graph showing the photoluminescence quantum efficiency.
Figure 9 shows Cs ₂ MnBr ₄ of Preparation Example 1 It shows the diffuse reflectance spectrum for the phosphor powder.
Figure 10 shows Cs ₂ MnBr ₄ of Preparation Example 1 It shows a graph showing the results of TRPL (Time-resolved photoluminescence spectroscopy) analysis of phosphor powder and InP phosphor powder.
Figure 11 shows Cs ₂ MnBr ₄ of Preparation Example 1 Change in luminescence intensity during the temperature increase and cooling process of the phosphor powder (a, b), relative luminescence intensity by temperature to the luminescence intensity at room temperature (c), luminescence intensity by temperature of Cs ₂ MnBr ₄ and other phosphors in Preparation Example 1 Shows graphs representing change (d).

Hereinafter, in order to explain the present invention in more detail, preferred embodiments according to the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

Throughout the specification of the present application, when a part is said to “include” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

The terms "about", "substantially", etc. used throughout the specification herein are used to mean at or close to the numerical value when a material tolerance is presented in the stated meaning, and are used accurately or closely to aid the understanding of the present application. Absolute values are used to prevent unscrupulous infringers from taking unfair advantage of the stated disclosure.

The light emitting body according to an embodiment of the present invention may include a compound represented by the following formula (1).

[Formula 1]

A ₂ Mn ₍ X ¹ _{1 -} ^a

In Formula 1, A may be at least one of alkali metal elements, specifically Li, Na, K, Rb, and Cs. X ¹ and X ² are different halogen ions. For example, X ¹ may be Br and X ² may be Cl or F. a may be 0 to 0.3. A may be a monovalent cation, Mn may be a divalent cation, and X ¹ and X ² may be monovalent anions. These compounds are metal halides containing Mn as a divalent metal, and do not contain lead, so they may not be harmful to the environment.

Specifically, a may have a value greater than 0 and less than 0.3. More specifically, the lower limit of the value of a may be 0.01, 0.03, 0.05, 0.07, 0.09, or 0.1. The upper limit of the a value may be 0.25, 0.23, 0.21, 0.2, 0.17, 0.15, 0.13, or 0.11.

The compound represented by Formula 1 may be a compound represented by Formula 2 below.

[Formula 2]

Cs ₂ Mn(X ¹ _1-a X ² _a ) ₄

The compound of Formula 2 is when A in Formula 1 is Cs.

Figure 1 shows the crystal structure of the compound represented by Formula 1 or Formula 2.

Referring to FIG. 1, the compound represented by Formula 1 or Formula 2 has an orthorhombic crystal structure and may have a space group of Pnma. In particular, the compound represented by Formula 1 or Formula 2 may exhibit a crystal structure of β-K ₂ SO ₄ . Specifically, MnX ₄ ^tetrahedra with Mn ²⁺ at the center and four

Here, the distance between a pair of Mn ²⁺ , which is the emission center, is relatively long, about 8 to 12 Å, so that excellent luminescence characteristics and high thermal stability can be achieved. In particular, when the compound is Cs ₂ MnBr ₄ , the distance between Mn ²⁺ may be 8.2 Å or 11.2 Å.

The compound can be obtained as a powder by grinding, and before grinding, it is synthesized in the form of agglomeration with a smooth surface like glass. After grinding, it is possible to obtain an It can be ceramic). In the case of such glass ceramics, the time required for synthesis is relatively short compared to single crystals, so there is less time for impurities to flow in, which has the advantage of being able to obtain high purity. Additionally, the compound may contain particles with a diameter of hundreds of nm.

In addition, in the present example, in the compound represented by Formula 1, Mn ²⁺ has electrons arranged in five 3d orbitals, and when binding to a ligand, the dz ² and dx ² -y ² orbitals and the dxy, dyz, and dxz orbitals are Crystal field splitting, in which energy is separated, may occur. In particular, when Mn ²⁺ combines with four ligands to form a tetrahedral structure, the dz ² and dx ² -y ² orbitals form a low energy level (e), and the dxy, dyz, and dxz orbitals form a high energy level (t2). ) to form.

Due to this crystal field separation, the compound can have a band gap of about 2.3 to 2.4 eV. Accordingly, the compound emits light in the ultraviolet to blue region, specifically 200 to 500 nm, more specifically 370 to 490 nm, for example, when light of 450 to 480 nm is incident, light in the green region, specifically about 510 to 530 nm. For example, it may emit light of 515 to 525 nm. In addition, the emission peak is several tens of nm, for example, 20 to 50 nm, specifically 30 to 45 nm, and has a small half width of 33 to 40 nm, thereby showing excellent color purity.

In one example, when a is 0 in Formula 1, that is, when a has a value greater than 0 and less than 0.3 compared to the state in which Br is not substituted with F or Cl, the photoluminescence quantum efficiency may be better, In particular, when a has a value near 0.1, excellent photoluminescence quantum efficiency of about 70% can be achieved. This can be seen as the result of the crystal being most stabilized by containing an appropriate amount of F ^- or Cl ^- , which has a higher ionic binding energy to the crystal frame compared to Br ^- .

The compound has a very short fluorescence lifetime of several hundred ps, specifically about 100 to 500 ps, for example, about 150 to 250 ps, so it may not leave an afterimage when applied to a display, which may be advantageous for high-speed video implementation. In addition, the compound can maintain luminescent properties, such as exhibiting a photoluminescence quantum efficiency of about 80% compared to room temperature, even at a high temperature of about 200° C., so it can have excellent thermal stability.

Figure 2 shows the crystal structure (a), electron configuration in the valence band (VBM) and conduction band (CBM), and electronic density of state (density of state) of Cs ₂ MnBr ₄ according to an embodiment of the present invention. DOS) (c), and band gap (d) are shown.

Referring to FIG. 2, based on density functional theory (DFT), it can be seen that the band gap between the valence band and conduction band of Cs ₂ MnBr ₄ according to this example is 5.7 eV. However, since the compounds represented by Formula 1 or Formula 2 according to embodiments of the present invention emit green light, this means that such green light emission is not due to the band gap between the valence band and conduction band of the compound. do.

Figure 3 is a schematic diagram showing the emission color according to the crystal field force (△) for each polyhedral structure of Mn ²⁺ ions.

Referring to Figure 3, the crystal field splitting of the d orbital of the Mn ²⁺ ion is dependent on the crystal field force (Δ), and the crystal field force (Δ) is formed with the ligands of the Mn ²⁺ ion. It appears differently depending on the polyhedral structure. Specifically, as the number of bonds between Mn ²⁺ ions and ligand ions increases, in other words, compared to the tetrahedral structure obtained by Mn ²⁺ ions bonded with 4 ligand ions, Mn ²⁺ ions bond with 6 ligand ions, In the case of the obtained octahedral structure, the crystal field force (Δ) increases. Accordingly, when the Mn ²⁺ ion is located in a tetrahedral structure due to the dd transition between ^{the 4} T ₁ and ⁶ A ₁ levels, the emission color is green, and when it is located in the octahedral structure, it has red emission characteristics.

Through this, the compound represented by Formula 1 or Formula 2 according to embodiments of the present invention has MnX ₄ tetrahedra in the crystal structure with Mn ²⁺ at the center and four Xs located at each vertex, ⁴ T ₁ It can be seen that green light is emitted due to the dd transition between the and ⁶ A ₁ levels.

In particular, in Mn ²⁺ , as five electrons are placed one by one in five 3d orbitals, this crystal field separation occurs and separated energy levels are formed within the bandgap, making the visible visible by the transition between the separated energy levels. Rays of light are emitted. On the other hand, in cases such as Cu ²⁺ and Zn ²⁺ , crystal field separation occurs, but the energy level caused by this crystal field separation is not located inside the band gap, or visible light is not emitted due to the transition between the separated energy levels. No. In cases such as Pb ²⁺ and Sn ²⁺ , crystal field separation does not occur because the 3d orbital is not involved in binding to the ligand.

The compound may exhibit photoluminescence (PL) properties and electroluminescence (EL) properties.

When using the photoluminescence properties of the compound, an ultraviolet or blue light emitting layer; And an optical device including a layer containing the compound disposed on the blue light-emitting layer can be implemented. The optical element may be a backlight unit (BLU) or a display. Specifically, the compound can be used in a backlight unit (BLU) or as a color converter in a display. In the case of use in BLU, as an example, a color conversion film in which the green light-emitting compound is dispersed along with a red light emitter (ex. red light-emitting phosphor or red light-emitting quantum dot) on a blue LED (Light Emitting Diode) backlight as an example of a blue light-emitting layer. It may be applied. When used as a color conversion layer, the green light-emitting compound may be placed on a blue OLED (Organic Light Emitting Diode) or blue nanorod LED.

Meanwhile, when using the electroluminescence properties of the compound, the compound can be applied to an electroluminescence display device that is interposed between an anode and a cathode and emits light by recombination of holes and electrons injected from the anode and the cathode.

Compounds according to Formula 1 or 2 can be obtained through the following production method.

First, a mixture can be obtained by mixing the raw materials AX ¹ , AX ² , MnX ¹ ₂ , and MnX ² ₂ at a stoichiometric equivalent ratio, specifically a molar ratio of 2-2a:2a:1-a:a. At this time, X ¹ and X ² may be as defined in Formula 1 above. Specifically _, in _the ^{case of a} compound such as Formula ² , Cs You can.

The mixing process can be performed in an inert gas atmosphere, such as argon. Specifically, the mixing process can be performed by mixing and pulverizing the raw materials at the molar ratio in a glove box filled with argon using an agate pestle and mortar to obtain a mixture. The mixing may proceed from 15 minutes to 1 hour.

The compound according to Formula 1 or 2 can be obtained by calcining the mixture in an inert gas atmosphere or reducing atmosphere and then naturally cooling it. The inert gas atmosphere may be an argon atmosphere, and the reducing atmosphere may be a hydrogen atmosphere. The firing can be performed after filling the mixture in an alumina crucible and placing the crucible filled with the mixture in an alumina tube electric furnace. In addition, the firing can be performed by raising the temperature to about 600 to 700°C, specifically, 625 to 675°C, and can be performed by maintaining the elevated temperature for 10 to 26 hours, specifically, 23 to 25 hours after the temperature increase is completed. there is.

Powder can be obtained by grinding the naturally cooled compound.

Below, a preferred experimental example (example) is presented to aid understanding of the present invention. However, the following experimental examples are only intended to aid understanding of the present invention, and the present invention is not limited by the following experimental examples.

Preparation Example 1: Cs ₂ MnBr ₄ Phosphor powder manufacturing

As raw materials, CsBr and MnBr ₂ powder were quantified at a stoichiometric equivalent molar ratio of 2:1, and then the quantified raw materials were agated in a glove box filled with an argon atmosphere. A mixture was obtained by mixing and grinding for 30 minutes using a pestle and mortar. After filling the crucible with the mixture, the crucible filled with the mixture was placed in an alumina tube electric furnace, heated to 650° C. under an argon atmosphere, maintained for 24 hours, fired, and then naturally cooled for 24 hours. Afterwards, the resulting product was pulverized to obtain Cs ₂ MnBr ₄ phosphor powder.

Preparation examples 2 to 4: Cs ₂ Mn(Br _1-a Cl _a ) ₄ Phosphor powder manufacturing

As raw materials, Cs ₂ Mn was prepared in a similar manner to Preparation Example 1, except that CsBr, CsCl, MnBr ₂ , and MnCl ₂ powder were prepared in a stoichiometric equivalent molar ratio of 2-2a:2a:1-a:a. (Br _1-a Cl _a ) ₄ Phosphor powder was obtained.

Table 1 below shows the composition of the phosphor powder according to Preparation Examples 1 to 4.

Furtherance a value in the formula Cs ₂ Mn(Br _1-a Cl _a ) ₄ for the total number of moles of Br and Cl
mol% of Cl Manufacturing Example 1 Cs ₂ MnBr ₄ 0 0 Production example 2 Cs ₂ MnBr _3.6 Cl _0.4 0.1 10 Production example 3 Cs ₂ MnBr _3.2 Cl _0.8 0.2 20 Production example 4 Cs ₂ MnBr _2.8 Cl _1.2 0.3 30

Figure 4 shows optical photos taken before and after pulverization after cooling during the manufacturing process of the Cs ₂ MnBr ₄ phosphor powder of Preparation Example 1.

Referring to FIG. 4, it can be seen that before pulverization, the Cs ₂ MnBr ₄ phosphor is synthesized in a lumped form with a smooth surface like glass and has a light yellow color.

Figure 5 shows a TEM (Transmission Electron Microscope) image (a), a lattice fringe image (b), and a Selected Area Electron Eiffraction pattern (SAED pattern) (c) of the Cs ₂ MnBr ₄ phosphor particles of Preparation Example 1. and EDX mapping (Energy-dispersive X-ray mapping).

Referring to Figure 5, it can be seen that irregularly shaped particles were formed. The diameter of this particle is several hundred nm, and it is a particle rather than a quantum dot. Additionally, this particle has crystal planes of (013), (004), (301), (122), (311), (221), (303), (223), and (321), and the (013) plane It can be seen that the spacing between the (221) planes is 0.391 nm and the spacing between the (221) planes is 0.301 nm. Additionally, it can be seen that Cs, Mn, and Br are uniformly distributed within the particles.

Figure 6 shows Cs ₂ Mn (Br _1-a Cl _a ) ₄ of Preparation Examples 1 to 4 (a=0, 0.1, 0.2, and 0.3) shows the X-ray diffraction pattern for the phosphor powder.

Referring to FIG. 6, a solid solution can be formed even in the case of Cs ₂ Mn(Br _1-a Cl _a ) ₄ (a=0.1, 0.2, and 0.3), so that Cs ₂ MnBr ₄ (a=0) It has the same crystal structure as in This crystal structure is orthorhombic and the space group is Pnma. In this way, the fact that the crystal structure is maintained even when a relatively large amount of Br ^- is replaced ^{with Cl - is} considered to be the result of reduced ion movement because the ionic binding energy of Cl ^- to the crystal frame is increased compared to Br -. You can.

However, when the Cl ^- ion concentration, that is, the a value, increased beyond 0.3, impurities were formed and the solid solution was not maintained.

Referring to FIGS. 4 and 6 simultaneously, Cs ₂ Mn(Br _1-a Cl _a ) ₄ of Preparation Examples 1 to 4 (a=0, 0.1, 0.2, and 0.3) Before grinding, the phosphor powder is synthesized in the form of agglomerates with a smooth surface like glass, and after grinding, an XRD pattern like a polycrystal can be obtained, indicating that it is glass rather than a single crystal. It can be seen that it is ceramic (glass ceramic).

In addition, the Cs ₂ MnBr ₄ phosphor of Preparation Example 1 had light yellow particles, whereas the Cl-doped Preparation Examples 2 to 4 showed green particles.

Figures 7 and 8 show Cs ₂ Mn (Br _1-a Cl _a ) ₄ of Preparation Examples 1 to 4, respectively. (a=0, 0.1, 0.2, and 0.3) This is a graph showing the optical properties of the phosphor powder and a graph showing the photoluminescence quantum efficiency. Specifically, the phosphor powder of each preparation example was irradiated with an excitation wavelength of 470 nm, and then a photoluminescence spectrum was obtained.

Referring to Figures 7 and 8, Cs ₂ Mn (Br _1-a Cl _a ) ₄ of Preparation Examples 1 to 4 (a=0, 0.1, 0.2, and 0.3) It can be seen that the phosphor powder emits green light with a wavelength of 520 nm. In addition, it was interpreted that there was almost no change in the position of the emission peak with respect to the change in a value, that is, the Cl content.

It can be seen that the luminous efficiency is better in the case of Cs ₂ Mn (Br _1-a Cl _a ) ₄ (a = 0.1, 0.2, and 0.3) in which Cl is substituted in the Br position compared to Cs ₂ MnBr ₄ (a = 0). . In particular, when Cl ^- is 10%, that is, when Cs ₂ Mn(Br _1-a Cl _a ) ₄ (a=0.1), the highest luminous efficiency, specifically the absolute photoluminescence quantum yield of about 70%. ), and the half width of the 520 nm emission peak was approximately 38 nm.

The highest luminous efficiency when about 10 at% of Br ^- is substituted with ^Cl - can be seen as the result of the crystal being most stabilized by containing an appropriate amount of Cl ^- , which has a high ionic binding energy to the crystal frame.

Figure 9 shows Cs ₂ MnBr ₄ of Preparation Example 1 It shows the diffuse reflectance spectrum for the phosphor powder.

Referring to Figure 9, it can be seen that when the band gap is calculated from the obtained diffuse reflection spectrum using the Kubelka-Munk theory, approximately 5.7 eV and approximately 2.4 eV are derived. At this time, the band gap of about 2.4 eV was interpreted to be due to splitting of the Mn ²⁺ 3d ⁵ energy level in Cs ₂ MnBr ₄ , and the emission wavelength of the phosphor powder according to this example was a band of about 2.4 eV. It is due to the gap.

Figure 10 shows Cs ₂ MnBr ₄ of Preparation Example 1 It shows a graph showing the results of TRPL (Time-resolved photoluminescence spectroscopy) analysis of phosphor powder and InP phosphor powder.

Referring to FIG. 10, the green InP quantum dots have a fluorescence lifetime of 6 ns, while the Cs ₂ MnBr ₄ of Preparation Example 1 The phosphor powder showed a fluorescence lifetime of 220 ps.

Figure 11 shows Cs ₂ MnBr ₄ of Preparation Example 1 Changes in luminescence intensity during the temperature increase and cooling process of the phosphor powder (a, b), relative luminescence intensity at room temperature (c), luminescence intensity at different temperatures for Cs ₂ MnBr ₄ and other phosphors in Preparation Example 1. Shows graphs representing change (d).

Referring to Figure 11, Cs ₂ MnBr ₄ of Preparation Example 1 In the process of heating and cooling the phosphor powder from room temperature to 200 ℃, the luminescence intensity decreases as the temperature increases, but when the luminescence intensity at room temperature is 100%, at 200 ℃, the luminescence intensity is 80%, so the phosphor according to this example It can be seen that the powder has excellent thermal stability. In addition, it can be seen that the same luminous intensity is shown at the same temperature during the heating and cooling process (a, b, c).

It can be seen that these characteristics are thermally much more stable results when compared to InP quantum dots and CsPbBr ₃ perovskite quantum dots. Although the thermal stability of InP quantum dots is superior to that of CsPbBr ₃ perovskite quantum dots, quantum dots represented by InP (Indium phosphate) have many surface defects due to their high surface area to volume ratio, resulting in charge traps (the main cause of reduced luminous efficiency). It is known to have a relatively low photoluminescence quantum yield (PLQY) due to the occurrence of trap phenomenon and non-radiative recombination.

Above, the present invention has been described in detail with preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes can be made by those skilled in the art within the technical spirit and scope of the present invention. This is possible.

Claims (17)

A metal halide comprising a compound represented by the following formula (1), having an orthorhombic crystal structure, and having a space group of Pnma:
[Formula 1]
A ₂ Mn ₍ X ¹ _{1 -} ^a
In Formula 1, A is an alkali metal element, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3. According to paragraph 1,
The compound represented by Formula 1 is a metal halide, which is a compound represented by Formula 2:
[Formula 2]
Cs ₂ Mn(X ¹ _1-a X ² _a ) ₄
In Formula 2, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3. According to paragraph 2,
In Formula 2, a is a metal halide greater than 0 and less than 0.3. According to paragraph 2,
In Formula 2, a is a metal halide of 0.01 to 0.2. According to paragraph 2,
In Formula 2, a is a metal halide of 0.05 to 0.15. According to paragraph 1,
The compound is a metal halide having the same crystal structure as β-K ₂ SO ₄ . According to paragraph 1,
The compound is a metal halide having a crystal structure with Mn ²⁺ at ^the center and MnX ₄ tetrahedra with ^{four X 1 ,} According to claim 1 or 7,
The compound is a metal halide that emits light in the green region by a dd transition between ^{the 4} T ₁ and ⁶ A ₁ levels. According to paragraph 1,
The compound is a metal halide that is glass ceramic. A color conversion method for obtaining light in the green region by irradiating incident light in the ultraviolet to blue region to the compound of claim 1. According to clause 10,
A color conversion method wherein the incident light is light of 370 to 490 nm. Blue emitting layer; and
An optical device comprising a layer containing the compound of claim 1 disposed on the blue light-emitting layer. According to clause 12,
The optical element is a backlight unit (BLU) or a display. Obtaining a mixture by mixing raw materials AX ¹ , AX ² , MnX ¹ ₂ , and MnX ² ₂ in a stoichiometric equivalent ratio; and
It includes the step of calcining the mixture in an inert gas atmosphere or reducing atmosphere and then naturally cooling to obtain a compound according to the following formula (1), wherein the compound has an orthorhombic crystal structure and a space group of Pnma. Metal halide production method having:
[Formula 1]
A ₂ Mn ₍ X ¹ _{1 -} ^a
In Formula 1, A is an alkali metal element, X ¹ is Br, X ² is Cl or F, and x is 0 to 0.3. According to clause 14,
A method of producing a metal halide where the calcination is carried out by raising the temperature to 600 to 700°C and maintaining it for 10 to 25 hours. According to clause 14,
The A is Cs,
The step of obtaining ^the mixture is ^{a step of} obtaining _a mixture by _mixing Cs
The compound represented by Formula 1 is a method of producing a metal halide, which is a compound represented by Formula 2:
[Formula 2]
Cs ₂ Mn(X ¹ _1-a X ² _a ) ₄
In Formula 2, X ¹ is Br, X ² is Cl or F, and a is 0 to 0.3. According to clause 14,
The compound is a glass ceramic metal halide manufacturing method.